The technique of reacting butadiene, acetic acid, and oxygen in the presence of a solid catalyst containing palladium to yield diacetoxybutene is known. Since the reaction proceeds in a liquid phase, it is important for efficiently carrying out the reaction to accelerate oxygen transfer from the gaseous phase to the liquid phase and thereby maintain a high oxygen concentration in the liquid phase.
Diacetoxybutene has hitherto been produced by a method of reaction in which a catalyst is disposed as a fixed bed in an oxygen-containing atmosphere and a liquid comprising butadiene and acetic acid is caused to flow down along the surface of the catalyst (see, for example, Japanese Patent Publication No. 42057/1980). This method of reaction, however, has the danger of generating an explosive mixed gas because the butadiene and acetic acid, which are liquid feed materials, partly vaporize and come into the oxygen-containing atmosphere, which is a continuous phase. Consequently, it has been necessary to regulate the oxygen concentration in the atmosphere so as to be lower than the lower explosion limit. It is a matter of course that low oxygen concentrations in the atmosphere constitute an obstacle to the acceleration of oxygen dissolution in the liquid.
In Japanese Patent Laid-Open No. 129514/1975 is disclosed a process for continuously producing diacetoxybutene which comprises feeding butadiene, acetic acid, and oxygen as upward cocurrent flows to a reactor in the presence of a fixed-bed catalyst comprising a supported palladium catalyst. However, this process, in which a gas containing oxygen is supplied to the liquid feed materials constituting a continuous phase, has the following drawbacks. The gas forms large bubbles and these bubbles are apt to coalesce with one another. Because of this, the area of the gas/liquid interface is apt to become small. Since the dissolution of oxygen in the feed liquid which is being fed to the fixed-bed catalyst is hence insufficient, the oxygen concentration in the liquid is insufficient, resulting in a reduced reaction efficiency. Furthermore, there is the danger of generating an explosive mixed gas because butadiene and acetic acid, which are liquid feed materials, partly vaporize and come into the bubbles. Consequently, as in the case of the method of reaction described above in which feed materials are caused to flow down, the oxygen concentration in the bubbles should be kept lower than the lower explosion limit and this is an obstacle to the acceleration of oxygen dissolution in the liquid.
A subject for the invention is to provide a method for efficiently reacting butadiene to produce diacetoxybutene in high yield, and to provide others.